Phase I study of [131I] ICF01012, a targeted radionuclide therapy, in metastatic melanoma: MELRIV-1 protocol

Background Benzamide-based radioligands targeting melanin were first developed for imaging melanoma and then for therapeutic purpose with targeted radionuclide therapy (TRT). [131I]ICF01012 presents a highly favorable pharmacokinetics profile in vivo for therapy. Tumour growth reduction and increase survival have been established in preclinical models of melanoma. According the these preclinical results, we initiate a first-in-human study aimed to determine the recommended dose of [131I]ICF01012 to administer for the treatment of patients with pigmented metastatic melanoma. Methods The MELRIV-1 trial is an open-label, multicentric, dose-escalation phase I trial. The study is divided in 2 steps, a selection part with an IV injection of low activity of [131I]ICF01012 (185 MBq at D0) to select patients who might benefit from [131I]ICF01012 TRT in therapeutic part, i.e. patient presenting at least one tumour lesion with [131I]ICF01012 uptake and an acceptable personalized dosimetry to critical organs (liver, kidney, lung and retina). According to dose escalation scheme driven by a Continual Reassessment Method (CRM) design, a single therapeutic injection of 800 MBq/m2, or 1600 MBq/m2, or 2700 MBq/m2 or 4000 MBq/m2 of [131I]ICF01012 will be administered at D11 (± 4 days). The primary endpoint is the recommended therapeutic dose of [131I]ICF01012, with DLT defined as any grade 3-4 NCI-CT toxicity during the 6 weeks following therapeutic dose. Safety, pharmacokinetic, biodistribution (using planar whole body and SPECT-CT acquisitions), sensitivity / specificity of [131I]ICF01012, and therapeutic efficacy will be assessed as secondary objectives. Patients who received therapeutic injection will be followed until 3 months after TRT. Since 6 to 18 patients are needed for the therapeutic part, up to 36 patients will be enrolled in the selection part. Discussion This study is a first-in-human trial evaluating the [131I]ICF01012 TRT in metastatic malignant melanomas with a diagnostic dose of the [131I]ICF01012 to select the patients who may benefit from a therapeutic dose of [131I]ICF01012, with at least one tumor lesion with [131I]ICF01012 uptake and an acceptable AD to healthy organ. Trial registration Clinicaltrials.gov: NCT03784625. Registered on December 24, 2018. Identifier in French National Agency for the Safety of Medicines and Health Products (ANSM): N°EudraCT 2016-002444-17.


Background
Melanoma is a cancer arising from skin melanocytes but mucosal or uveal forms exist [1]. Surgical excision represents the first-line treatment for melanoma [2]. Depending on TNM staging, adjuvant immunotherapy or targeted therapy could be proposed to lower the metastatic risk [3]. However, melanoma is a highly metastatic cancer and represents a major public health problem for many years. Until 2010, only chemotherapies were available to treat metastatic melanomas and prognostic was poor [4]. MAPK pathway targeted therapies including BRAF V600E [5] and MEK-activated proteins [6] and immunotherapies with antibody against immune check-point inhibitors such as CTLA-4 [4], PD-1 [7] and its ligand PD-L1, have completely modified metastatic melanoma prognosis. However, patients can be nonresponders or develop some resistance [8]. Therefore, it is still mandatory to develop new therapeutic strategies as external stereotactic radiation therapy, alone or combined with systemic treatments. Targeted radionuclide therapy (TRT) [9], a nuclear medicine strategy that consists in administering a radiopharmaceutical compound to the patient in order to deliver a high absorbed dose of radiation to tumours while avoiding or minimizing normal tissue toxicities, could be one of them.
Multiples approaches have been developed in this field [9,10], using melanin targeting by antibodies or small molecules (benzamides), or MSH analogs (peptides), or membrane receptors targeting (antibodies). A few have been tested in human with mixed results [9,10]. Only a phase I trial has tested a benzamide radiolabeled with iodine-131 on a series of 26 patients with metastatic malignant melanoma [11]. All received a diagnostic dose of 235 ± 62 MBq of [ 123 I]-BA52 for planar and SPECT/ CT imaging, and only 9 patients were selected to receive a radionuclide therapy with a single dose of [ 131 ] I-BA52 with different activity levels between 510 to 6600 MBq. A specific uptake and long-term retention in tumor tissue with low transient uptake in the excretory organs was observed with diagnostic injection of [ 123 ] I-BA52. The highest estimated dose to a normal organ was found for the lung (mean, 3.1 Gy/GBq). No relevant acute or midterm toxicity was observed with the administered doses. In tumor tissue, a maximum dose of 12.2 Gy per GBq of [ 131 ] I-BA52 was calculated. Among the 5 patients who received [ 131 ] I-BA52 dose > 4.3 GBq (potentially effective), 3 demonstrated a surprisingly long survival of more than 2 years. These results highlight the potential of small molecule with high melanin affinity for TRT to treated metastatic melanoma.
Since 1990's, our team has developed several compounds displaying a high affinity for melanin, benzamidederived melanin-targeting molecules for imaging and/ or therapy [12][13][14]. BZA and BZA2 radiolabeled with iodine-123 have been clinically tested for a diagnostic approach for SPECT imaging of metastatic melanoma leading to phase II clinical trials [15,16]. In a prospective and multicentric phase III clinical study comparing [ 123 I] BZA2 scintigraphy to [ 18 F]-FDG PET-CT for melanoma staging (n = 87), the sensitivity and specificity of BZA2 for the diagnosis of pigmented lesions were 85 and 76% [17].
ICF01012 is a pharmacomodulated form of this BZA2, with highly favorable pharmacokinetics in murine models for therapy, with a long-lasting tumoral intake (8 days) and a rapid elimination of non-target organs (< 24 h) [18]. The TRT efficiency of [ 131 I]ICF01012 have been achieved on syngeneic murine models (B16F0 and B16Bl6) and murine model bearing xenografts (SK-Mel 3). With single or multiple injection of [ 131 I]ICF01012, a slowing of tumor growth and an increase in survival were observed [19][20][21]. A clear relationship between the presence of melanins and the efficacy of therapy has also been demonstrated. Radiotoxicity studies conducted with [ 131 I] ICF01012 at a therapeutic dose on highly pigmented mouse models have shown a transient decrease in white blood cells and a relative decrease in the thickness of the retina [22]. Dosimetry extrapolations have shown retina-values below the maximum tolerated doses, suggesting that this ocular specific targeting is not expected to have an impact in human [23]. Furthermore, preliminary toxicological studies point out that TRT with [ 131 I] ICF01012 was compatible with clinical requirements. Impact of TRT using [ 131 I]ICF01012 has also been evaluated on metastasis mechanisms [24] and current melanoma treatments (immune checkpoints inhibitors [25] and MAPK targeted therapies [26]) in murine melanoma models. According

Study design
This is an open-label, multicentric, "first-in-human", dose-escalation phase I trial of a radiopharmaceutical.
The study based on a theranostic approach is divided in 2 steps: The duration of intervention for each patient will be 7 days (diagnostic phase only) or 3 weeks (diagnostic phase + therapeutic phase). Follow-up will last 4 weeks (diagnostic phase only) or 10 weeks (diagnostic phase + therapeutic phase).

Coordination and participating institutions
The Centre Jean Perrin is the sponsor and responsible for the coordination of the trial, data management, monitoring and statistical analysis.
The multicenter study is currently conducted at 2 sites in France: the University Hospital of Clermont-Ferrand and the Centre Jean Perrin. Patients with cutaneous melanomas will be recruited at the Dermatology and Oncodermatology Department of the University Hospital of Clermont-Ferrand and patients with uveal melanomas will be recruited at the Jean Perrin Cancer Center. For all patients, targeted radionuclide therapy will be performed at the Nuclear Medicine Department of the Jean Perrin Cancer.

Main objective
The primary objective is to determine the recommended dose of [ 131 I]ICF01012 to use for pigmented melanoma metastases TRT.
The primary endpoint is the recommended therapeutic dose of [ 131 I]ICF01012, defined as the higher dose for which the percentage of dose-limiting toxicity (DLT) is lower than 33%. DLT is defined as any grade 3-4 NCI-CT toxicity, except for alopecia, nausea and vomiting or fever, which can be managed by symptomatic treatment. Only toxicities experienced during the 6 weeks following therapeutic dose administration will be considered as DLT.

Secondary objectives
The secondary objectives and the corresponding endpoints are: -To determine the [ 131 I]ICF01012 sensitivity and specificity in a patient-based analysis and in a lesionbased analysis.
[ 131 I]ICF01012 sensitivity and specificity in patientbased analysis and in lesion-based analysis will be quantified by comparison of visualized or non-

Study drug and premedication administration
Selection part The diagnostic dose of [ 131 I]ICF01012 labeled with an activity of 185 MBq will be administered by slow intravenous injection in a approximatively 10 min at D0 in the presence of a nuclear medicine physician.
Patients will receive per os premedication of potassium iodide 130 mg of 48 h before [ 131 I]ICF01012 injection, and of loratadine 10 mg and potassium iodide 130 mg, 24 h before [ 131 I]ICF01012 injection. The day of the injection, oral potassium iodide 130 mg will be taken approximatively 4 h before injection and IV premedication (dexchlorpheniramine 5 mg and hydrocortisone hémisuccinate 500 mg) 5 minutes before injection. Thyroid blockade will be pursued for a period of 8 days (D1-D8) (potassium iodide 130 mg daily).
Therapeutic part According to the dose escalation scheme, a single therapeutic injection of 800 MBq/m 2 , or 1600 MBq/m 2 , or 2700 MBq/m 2 or 4000 MBq/m 2 of [ 131 I] ICF01012 will be administered at D11 (± 4 days) under the same conditions as those for diagnostic injection (slow IV injection in approximatively 10 min).
Before therapeutic injection of [ 131 I]ICF01012, patients will receive identical premedication as for the diagnostic injection: potassium iodide 130 mg at 48 h before infusion, loratadine 10 mg and potassium iodide 130 mg 24 h before injection. The day of the injection, oral potassium iodide 130 mg will be taken approximatively 4 h before injection and IV premedication (dexchlorpheniramine 5 mg and hydrocortisone hémisuccinate 500 mg) 5 minutes before injection. Thyroid blockade will be pursued for a period of 60 days (D12-D71) (potassium iodide 130 mg daily).

Study procedures and participant timeline
The overview of study assessments and procedures is detailed in Table 1 for patients who participate only to the selection part, and in Table 2 for patients who participate to the selection part and the treatment part.
Before any study-related assessment starts, written informed consent will be obtained for each patient. A screening/baseline visit will include imaging for disease evaluation and a dosimetric whole-body CT-scan within 30 days before administration of the diagnostic dose (D0). Within 15 days before administration of the diagnostic dose, the patients will have a clinical evaluation with vital signs, cardiac evaluation, specialized consultation with a dermatologist, a neurologist and an ophthalmologist, blood and urine test and a pregnancy test (for women of childbearing age).
Patients are registered before the diagnostic dose (D0).    The eligibility criteria for therapeutic part (at least one metastasis with [ 131 I]ICF01012 uptake and an acceptable AD to major healthy organs) will be checked from D4 until D7 with dosimetry results. After verification of the eligibity criteria for therapeutic part, a dose allocation request will be done using an eCRF. Eligible patients for therapeutic phase will have an ocular optical coherence tomography (OCT) before therapeutic injection.
Therapeutic part A unique therapeutic injection of [ 131 I] ICF01012 at a dose level of 800 MBq/m 2 , or 1600 MBq/ m 2 , or 2700 MBq/m 2 or 4000 MBq/m 2 (according to dose escalation scheme), will be administered D11 ± 4 days with a follow-up of vital signs: before, 5 min after the start of infusion, at the end of infusion, 30 min, 1 h, 3 h, and 24 h (D12) after the end of infusion and then 2 days, 4 days, 5 days and 7 days after therapeutic dose. Patients will have to stay hospitalized between 3 and 7 days after injection, depending on received radioactivity, Patients will be discharged when 1-m rate of exposure reaches <40μSievert.h − 1 .
Follow-up Non-eligible patients for therapeutic part will be followed during 3 weeks: 2 follow-up visits are scheduled 14 days and 35 days after diagnostic dose injection for safety evaluation (clinical examination, vital measurement, blood and urinary analyses, specialized consultations (ophthalmologist, neurologist and dermatologist)).
For patient receiving the therapeutic dose, five followup visits are scheduled 14, 28, 42, 63 and 85 days after therapeutic dose injection. Each visit will include: clinical examination, vital measurement, blood and urinary analyses. Specialized consultations (ophthalmologist, neurologist and dermatologist) will occur 14 days after therapeutic dose and for dermatologist consultations 42 and 85 after therapeutic dose. Dosimetric acquisitions will be done on 14 and 63 after therapeutic dose (see below). Post-therapeutic cardiac evaluation (myocardial perfusion scintigraphy) and disease staging (cranial and thoraco-abdominopelvic CT scan and [ 18 F] FDG PET-CT) will be done 85 days after therapeutic dose.

Personalized dosimetry
The in vivo biodistribution of [ 131 I]ICF01012 will be assessed using planar whole body (2D) and thoraxabdomen-pelvis SPECT-CT acquisitions (3D). Planar and SPECT acquisitions will be performed following the Medical Internal Radiation Dose Committee (MIRD) guidelines for quantitative imaging with 131 I [28,29] on a Symbia Intevo T6 SPECT/CT (Siemens), equipped with HEGP collimators and 3/8″ NaI detector crystals. The time-integrated activity ∼ A(r S ) (or total number of nuclear transformations in source region r S ) will be calculated by fitting time-activity curves for each region previously segmented on CT scan. The time-integrated activity obtained for diagnostic part is then scaled with the expected injected activity for therapeutic part. The patient specific S-values (defined as absorbed dose in target region r T per nuclear transformation in source region r S ) will be computed by Monte-Carlo simulation using GATE. The mean absorbed dose to organs and tumours will be calculated using MIRD formalism [21]. According to this formalism, the mean absorbed dose is given by: The most unfavourable result of the dosimetry based on 2D or 3D imaging quantification will be retained.

Statistical considerations Sample size
Using a CRM model with 4 dose levels, i.e. with cohorts of one patient by dose level and at least 6 patients at the recommended dose, a minimum of 6 patients and a maximum of 18 patients should be included in the "therapeutic part". Sample size calculation for the selection part is based on the hypothesis that 50% of patients will have at least an [ 131 I]ICF01012 lesion uptake as observed with BZA2 in phase III study [8] and thus be eligible for the therapeutic part. Therefore, between 12 to 36 patients will be enrolled in the selection part in order to ensure the necessary sample size for the therapeutic part (between 6 to 18).

Data analysis
Due to the nature and the design of the study, statistical analysis will be mainly descriptive. Two populations will be analyzed: the diagnostic population (all participants who receive the diagnostic dose) and the therapeutic population (all participants who receive the therapeutic dose). The recommended therapeutic dose will be defined as the highest tested dose for which the percentage of DLT in the diagnostic population is lower than 33%. DLT percentage will be calculated for each tested dose. Only therapeutic population will be included in the analysis of DLT and the efficacy analysis. The statistical significance threshold is set at 5%. Statistical analyses will be performed using R software.

Data management and monitoring
Study data will be entered by investigator or delegate in an eCRF based on the Web-Based Data Capture (WBDC) system "Ennov Clincal". Health-related personal data captured during this study are strictly confidential and accessible only by investigators and authorized professionals who are subject to professional secrecy. The investigator ensures that pseudonymized patient data are recorded on eCRF and of the provision of answers to data queries.
Monitoring reviews (site monitoring and central data monitoring) will be regularly carried out by a clinical research associate mandated by the sponsor to ensure the respect of the study protocol and procedures therein, and the quality of the collected data (accuracy, missing data, consistency with the source documents). Monitoring reports will ensure traceability.

Independent data monitoring Committee (IDMC)
IDMC will be set up to assess the progress of the clinical trial, safety data, benefit/risk ratio of the trial and to recommend to the Sponsor whether to continue, modify, or stop the trial. Members composing the IDMC will be selected to have the relevant clinical trials/medical expertise without direct involvement in the conduct of the trial. The committee will include a nuclear physician and 2 oncologists. Given the very low number of expected DLT and the use of a CRM, the committee will meet for each observed DLT or every 5 patients treated at therapeutic dose in absence of DLT.

Trial status
The MELRIV-1 trial is currently recruiting. Participant recruitment began in October 2019 with a 33-month enrolment period and an estimated completion in November 2022. The approved protocol is version 7, 28 June 2021.

Discussion
The MELRIV-1 trial is the first in human evaluation of the [ 131 I]ICF01012 TRT in metastatic malignant melanomas. This study aims to determine the recommended dose of [ 131 I]ICF01012 to administer for the treatment of patients with pigmented metastatic melanoma (binding [ 131 I]ICF01012).
[ 131 I]ICF01012 is a melanin-targeting compound allowing both imaging and TRT [18]. Even though targeting melanin to destroy melanoma cells is a seducing approach, some concerns exist and have been taken in account for this study design. Firstly, melanoma cells can lose the ability to synthesize melanin during the dedifferentiation process [30]. BZA2 phase 3 studies showed that approximately 50% of metastatic lesions did not capture melanin radiotracer [17]. Secondly, melanin is also present in healthy organs and tissues, as skin (keratinocytes, naevi), eyes (retinal pigment epithelium), brain (basal ganglia), heart, and adipose tissues (morbid obesity) [31]. Moreover, classically, radiation sensitive organs in TRT are red bone marrow, kidneys and liver. A radiosensitivity inter-patient variation of 20% dose can exist [32].
The design chosen in this trial was based on a theranostic approach with a pre-treatment dosimetry, with an infra-therapeutic dose of the [ 131 I]ICF01012 that permits to select the patients who may benefit of a therapeutic dose of [ 131 I]ICF01012, with at least one tumour lesion with [ 131 I]ICF01012 uptake and an acceptable AD to healthy organ. Radiotoxicity must be minimized with a pre-treatment dosimetry. A precise dosimetry, i.e. the quantification of energy deposed in tumour and non-target organs, is the main concern for TRT evaluation in a clinical trial [21,23].
The used of radiolabelled benzamides may constitute a therapeutic solution for melanomas resistant to therapy (for review see [10]). Compared to external radiation beam therapy, TRT allows a systemic treatment of a polymetastatic disease. [ 131 I]ICF01012 is an original strategy for targeting pigmented lesions, but also unpigmented metastases through a potential abscopal effect [25].